Thanks to the laws of physics—specifically quantum entanglement—quantum cryptography promises to deliver unbreakable codes. Quantum physicist Artur Ekert explains how.
Watch the full program here: https://youtu.be/HWb0y5gY590
Original Program Date: May 31, 2015
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How do you secure messages over the internet? How do quantum computers break it? How do you fix it? Why don't you watch the video to find out? Why does this description have so many questions? Why are you still reading? What is the meaning of life?
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CLARIFICATIONS:
You don't actually need a quantum computer to do quantum-safe encryption. As briefly mentioned at 7:04 , there are encryption schemes that can be run on regular computers that can't be broken by quantum computers.
CORRECTIONS:
[2:18] Technically, you can use any key to encrypt or decrypt whatever you want. But there's a specific way to use them that's useful, which is what's shown in the video.
[5:36] In RSA, depending on exactly what you mean by "private key", neither key is actually derivable from the other. When they are created, they are generated together from a common base (not just the public key from the private key). But typically, the file that stores the "private key" actually contains a bit more information than just the private key. For example, in PKCS #1 RSA private key format ( https://tools.ietf.org/html/rfc3447#appendix-A.1.2 ), the file technically contains the entire public key too. So in short, you technically can't get the public key from the private key or vice versa, but the file that contains the private key can hold more than just the private key alone, making it possible to retrieve the public key from it.
Video links:
Encryption and HUGE numbers - Numberphile
https://youtu.be/M7kEpw1tn50
The No Cloning Theorem - minutephysics
https://youtu.be/owPC60Ue0BE
Quantum Entanglement & Spooky Action at a Distance - Veritasium
https://youtu.be/ZuvK-od647c
Sources:
Quantum Computing for Computer Scientists
http://books.google.ca/books/about/Quantum_Computing_for_Computer_Scientist.html?id=eTT0FsHA5DAC
Random person talking about Quantum MITM attacks
http://crypto.stackexchange.com/questions/2719/is-quantum-key-distribution-safe-against-mitm-attacks-too
The Ekert Protocol (i.e. E91)
http://www.ux1.eiu.edu/~nilic/Nina's-article.pdf
Annealing vs. Universal Quantum Computers
https://medium.com/quantum-bits/what-s-the-difference-between-quantum-annealing-and-universal-gate-quantum-computers-c5e5099175a1
Images, Documents, and Screenshots:
Post-Quantum Cryptography initiatives
http://csrc.nist.gov/groups/ST/post-quantum-crypto/cfp-announce-dec2016.html
http://pqcrypto.eu.org/docs/initial-recommendations.pdf
Internet map (Carna Botnet)
http://census2012.sourceforge.net/
Quantum network maps
https://www.slideshare.net/ADVAOpticalNetworking/how-to-quantumsecure-optical-networks
http://www.secoqc.net/html/press/pressmedia.html
IBM Quantum
http://research.ibm.com/ibm-q/
Music:
YouTube audio library:
Blue Skies
Incompetech:
Jay Jay
Pamgaea
The House of Leaves
Premium Beat:
Cutting Edge Technology
Second Time Around
Swoosh 1 sound effect came from here:
http://soundbible.com/682-Swoosh-1.html
...and is under this license:
https://creativecommons.org/licenses/sampling+/1.0/

Steve Flammia (University of Sydney)
Sparse Quantum Codes with (Almost) Good Distance
QuICS Workshop on the Frontiers of Quantum Information and Computer Science (September 29, 2015)
Sparse error correcting codes, where every parity check involves only a small (constant) number of bits, have become ubiquitous because they can be generated easily and decoded efficiently, even when a constant fraction of bits are in error.
These properties do not carry over easily to the quantum case, however. In this talk, I will discuss a family of quantum sparse codes that can correct a nearly constant fraction of errors. The codes are sparse enough that each syndrome measurement involves just three qubits at a time. The construction is very general, and proceeds by transforming any other quantum code into a sparse one. The price we pay for this transformation is some extra qubits and that the new code is a more general subsystem code. If time permits, I will also discuss the connection between these new codes and the physics of self-correcting quantum memories.
Joint work with D. Bacon, A. Harrow, and J. Shi (arXiv:1411.3334).

One of the strangest features of quantum mechanics is also potentially its most useful: entanglement. By harnessing the ability for two particles to be intimately intertwined across great distances, researchers are working to create technologies that even Einstein could not imagine, from quantum computers that can run millions of calculations in parallel, to new forms of cryptography that may be impossible to crack. Join us as we explore the coming age of quantum technology, which promises to bring with it a far deeper understanding of fundamental physics.
PARTICIPANTS: Jerry Chow, Julia Kempe, Seth Lloyd, Kathy-Anne Soderberg
MODERATOR: George Musser
Original program date: JUNE 3, 2017
FIND OUT MORE ABOUT THE PROGRAM AND PARTICIPANTS: https://www.worldsciencefestival.com/programs/the-qubit-revolution/
This program is part of the Big Ideas Series, made possible with support from the John Templeton Foundation.
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Introduction of Participants 00:25
Program Begins: Quantum mechanics, weird or unfamiliar? 01:38
How much power is 20 Qubit's? 10:28
What are the pros and cons of Superconducting quantum computing? 25:55
The factorization problem 40:01
Is there a relationship between quantum computing and machine learning? 48:31
Q & A 54:17
This program was filmed live at the 2017 World Science Festival and edited for YouTube.

This talk discards hand-wavy pop-science metaphors and answers a simple question: from a computer science perspective, how can a quantum computer outperform a classical computer? Attendees will learn the following:
- Representing computation with basic linear algebra (matrices and vectors)
- The computational workings of qbits, superposition, and quantum logic gates
- Solving the Deutsch oracle problem: the simplest problem where a quantum computer outperforms classical methods
- Bonus topics: quantum entanglement and teleportation
The talk concludes with a live demonstration of quantum entanglement on a real-world quantum computer, and a demo of the Deutsch oracle problem implemented in Q# with the Microsoft Quantum Development Kit. This talk assumes no prerequisite knowledge, although comfort with basic linear algebra (matrices, vectors, matrix multiplication) will ease understanding.
See more at https://www.microsoft.com/en-us/research/video/quantum-computing-computer-scientists/

What is computation? ...and what is quantum computation?
CORRECTIONS:
8:01 The Pauli-X gate does NOT flip the direction of the qubit. It rotates it 180 degrees about the x-axis, where the x-axis is pointing out of the screen.
9:41 This graph is wrong. The Shor curve should be below the Classical curve since it takes LESS time.
Sources:
Quantum Computing for Computer Scientists
http://books.google.ca/books/about/Quantum_Computing_for_Computer_Scientist.html?id=eTT0FsHA5DAC
Quantum Computers: Fundamentals, Application and Implementation
www.tngtech.com/assets/btd/btd6/BenjaminFeldman_BTD6.pptx
Quantum Computation Roadmap
qist.lanl.gov/qcomp_map.shtml
WATERLOO NEWS
https://uwaterloo.ca/news/news/experiment-opens-door-multi-party-quantum-communication
Engineer Guy
http://www.engineerguy.com/
Numberphile
http://www.numberphile.com/
Images:
Cat:
cheezburger.com/6403122944
Dog:
www.quickmeme.com/meme/3qmjkj
Loop Quantum Gravity:
commons.wikimedia.org/wiki/File:Loop_quantum_gravity.jpg
Billiard Ball Tube Gate:
http://commons.wikimedia.org/wiki/File:Toffoli_BilliardBall.gif
Republished under the terms of the Creative Commons Attribution-Share Alike 2.5 Generic license
http://creativecommons.org/licenses/by-sa/2.5/deed.en
Water Valve Gate:
http://en.wikipedia.org/wiki/File:Hydristor2.jpg
Republished under the terms of the GNU Free Documentation License
http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License
Boolean Algebra Book:
http://books.google.ca/books/about/An_Investigation_of_the_Laws_of_Thought.html?id=SWgLVT0otY8C&redir_esc=y
Music downloaded from the YouTube Audio Library:
Phase Three
The Messenger
Good Starts
Camaguey
First Day
Where I am From

We present a fault-tolerant universal gate set consisting of Hadamard and controlled-controlled-Z (CCZ) on Bacon-Shor subsystem codes. Transversal non-Clifford gates on these codes are intriguing in that higher levels of the Clifford hierarchy become accessible as the code becomes more asymmetric. For instance, in an appropriate gauge, Bacon-Shor codes on an m-by-mk lattice have transversal k-qubit-controlled Z. We also describe how, for any stabilizer code, logical operator asymmetry is a necessary condition for transversal gates in high levels of the Clifford hierarchy. For Bacon-Shor CCZ, through a variety of tricks, including intermediate error-correction and non-Pauli recovery, we reduce the overhead required for fault-tolerant implementation. We calculate pseudothresholds for our universal gate set on the smallest 3-by-3 Bacon-Shor code and also compare our gates with magic-states within the framework of a proposed ion trap architecture.
See more at https://www.microsoft.com/en-us/research/video/universal-fault-tolerant-computing-with-bacon-shor-codes/

I introduce practical attacks on quantum cryptography, and give several examples of attacks and countermeasures.
This is lecture 2 in the series, however if you are familiar with the basics of quantum cryptography (introduced in lecture 1 http://goo.gl/vue6U2), you can start with this lecture. More attack examples, and how the research and manufacturing community handles this security problem will be discussed in lecture 3 http://goo.gl/cQDzFg
Presentation slides of the entire lecture course can be downloaded at:
Power Point (95 MiB, with videos and animations) - http://www.vad1.com/lab/presentations/Makarov-20140801-IQC-short-course.pptx
PDF (14.8 MiB, static images only) - http://www.vad1.com/lab/presentations/Makarov-20140801-IQC-short-course.pdf
Vadim Makarov is a research assistant professor at the Institute for Quantum Computing, heading the Quantum hacking lab - http://www.vad1.com/lab/
This course was part of a lecture series hosted by CryptoWorks21 in August 2014 in Waterloo, Canada.
Find out more about IQC!
Website - https://uwaterloo.ca/institute-for-quantum-computing/
Facebook - https://www.facebook.com/QuantumIQC
Twitter - https://twitter.com/QuantumIQC

Video abstract for the article 'Long range failure-tolerant entanglement distribution' by Ying Li, Sean D Barrett, Thomas M Stace and Simon C Benjamin (Ying Li et al 2013 New J. Phys. 15 023012).
Read the full article in New Journal of Physics http://iopscience.iop.org/1367-2630/15/2/023012/article.
GENERAL SCIENTIFIC SUMMARY
Introduction and background. Distributing an entangled state among remote quantum computers is one of the fundamental tasks of quantum information technologies. It is crucial for quantum teleportation, quantum cryptography and distributed quantum computing. Using direct transmission, the success probability of transmitting a qubit and the fidelity of the resulting quantum state decrease exponentially with distance. Therefore, one needs quantum repeaters to achieve long distance entanglement. A good quantum repeater protocol should be fault-tolerant and support a high communication rate.
Main results. In this paper, we propose a protocol of distributing entanglement by single-qubit measurements on a topologically protected cluster state across the chain of repeater stations. In our protocol, the repeater stations may employ non-deterministic entanglement operations: that is, a means of entanglement, even within a single repeater, that often fails but the failures are 'heralded'. The protocol is valid if the probability of an error occurring in the communication channel connecting stations is lower than a threshold, which is 15% when errors induced by operations within repeaters are negligible. And, we find that the rate of distributing entanglement decreases only logarithmically with the communication distance.
Wider implications. Compared with previous protocols, ours is the first to consider a probabilistic architecture within each repeater station, so that the entanglement distribution can be efficient even if entanglement operations are far from deterministic, i.e. our protocol is less experimentally demanding.

Summing up why Hamming's error correcting codes are regarded as 'Perfect' - Professor Brailsford explains.
EXTRA BITS: https://youtu.be/i4zC67Yf5Iw
For more background on this: https://youtu.be/1_X-7BgHbE0
http://www.facebook.com/computerphile
https://twitter.com/computer_phile
This video was filmed and edited by Sean Riley.
Computer Science at the University of Nottingham: http://bit.ly/nottscomputer
Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com

Original post: https://www.gcppodcast.com/post/episode-123-post-quantum-cryptography-with-nick-sullivan-and-adam-langley/
Nick Sullivan, and Adam Langley join Melanie and Mark to provide a pragmatic view on post-quantum cryptography and what it means to research security for the potential of quantum computing. Post-quantum cryptography is about developing algorithms that are resistant to quantum computers in conjunction with “classical” computers. It’s about looking at the full picture of potential threats and planning on how to address them using a diversity of types of mathematics in the research. Adam and Nick help clarify the different terminology and techniques that are applied in the research and give a practical understanding of what to expect from a security perspective.

Quantum computers exploit the bizarre features of quantum mechanics to perform tasks that are impossible using conventional means. Sending instantaneous messages across long distances or quickly computing over ungodly amounts of data are just two possibilities that arise if we can design computers to exploit quantum uncertainty, entanglement, and measurement.
In this SFI Community Lecture, scientist Christopher Monroe describes the architecture of a quantum computer based on individual atoms, suspended and isolated with electric fields, and individually addressed with laser beams. This leading physical representation of a quantum computer has allowed demonstrations of small algorithms and emulations of hard quantum problems with more than 50 quantum bits. While this system can solve some esoteric tasks that cannot be accomplished in conventional devices, it remains a great challenge to build a quantum computer big enough to be useful for society. But the good news is that we don’t see any fundamental limits to scaling atomic quantum computers, and Monroe speculates as to how this might happen.
Christopher Monroe is a leading atomic physicist and quantum information scientist. He demonstrated the first quantum gate realized in any system at the National Institute of Standards and Technology (NIST) in the 1990s, and at University of Michigan and University of Maryland he discovered new ways to scale trapped ion qubits and simplify their control with semiconductor chip traps, simplified lasers, and photonic interfaces for long-distance entanglement. He received the American Physical Society I.I. Rabi Prize and the Arthur Schawlow Laser Science Prize, and has been elected into the National Academy of Sciences. He is Co-Founder and Chief Scientist at IonQ in College Park, MD.

"Quantum Origami: Fault-tolerant Transversal Gates for Quantum Computation and Measurement of Topological Order"
Speaker: Guanyu Zhu, JQI
Abstract: Topologically ordered states of matter arise both as ground states of strongly interacting many-body quantum Hamiltonians and also as code subspaces of quantum error correction codes. A conventional way to perform logical operations in this subspace is via adiabatic braiding of anyons which has a linear overhead with the system size or equivalently the code distance. An alternative way of doing these operations is via transversal logical gates (TLG). TLGs are inherently fault-tolerant due to the locality of error propagation, while their one-shot nature (constant circuit depth) dramatically speeds up the time to perform a logical operation. However, the current sets of TLGs are quite limited and cannot form a universal set. Moreover, there is a lack of deep understanding, on a fundamental level, of certain types of transversal gates, such as those in color codes.
In this talk, I discuss a wide class of TLGs using modular transformations, which are elements of the mapping class group (MCG) of a genus-g surface. In particular, by considering multiple layers of a topological state together with appropriate gapped boundaries or twist defects, it is possible to implement modular transformations such as S and T transversally by local SWAP gates between the layers. Our discovery also provides a simple geometric interpretation for a class of TLGs, i.e., “manifold origami”, involving folding of the manifold and permutation of code patches. This new scheme not only leads to a deep understanding of existing TLGs, but also greatly extends the variety of them, especially to the realm of non-abelian phases. In particular, TLGs in non-abelian systems, such as Fibonacci and Ising phases, can be used to perform a universal set of logical gates, without the requirement of state distillation. From an even broader perspective, we also reveal a deep connection between TLGs and anyon symmetry transformation in the context of symmetry-enriched topological phases. We propose an experimental implementation of these ideas using superconducting qubits, and also methods to measure the modular matrices, which contain the braiding statistics of quasiparticles.
"Transport Signatures of Dirac electrons in a random magnetic field"
Speaker: Hilary Hurst
Abstract: In this talk we consider the proximity effect between Dirac states at the surface of a topological insulator and a ferromagnet with easy plane anisotropy, which is described by the XY-model and undergoes a Berezinskii-Kosterlitz-Thouless (BKT) vortex unbinding phase transition. The surface states of the topological insulator interacting with classical magnetic fluctuations of the ferromagnet can be mapped onto the problem of Dirac fermions in a random magnetic field. However, this analogy is only partial in the presence of electron-hole asymmetry or warping of the Dirac dispersion, which results in screening of magnetic fluctuations. Scattering at magnetic fluctuations influences the behavior of the surface resistivity as a function of temperature. Near the BKT phase transition temperature we find that the resistivity of surface states scales linearly with temperature and has a clear maximum which becomes more pronounced as the Fermi energy decreases. Additionally at low temperatures we find linear resistivity, which is usually associated with non-Fermi liquid behavior but here it appears entirely within the Fermi liquid picture.

Mary Wootters
Assistant Professor, Computer Science and Electrical Engineering, Stanford University
ABSTRACT:
Error correcting codes are a tool for protecting information from noise. They show up all over the place, from cell phones to satellites to hard drives. In this lecture, I’ll introduce the basic concepts behind error correcting codes, and we’ll work through a concrete example called the Hamming Code. Then we will briefly cover some more modern developments in error correcting codes, motivated by applications in electrical engineering, computer science, mathematics, and beyond.
BIO:
Mary Wootters is an assistant professor of Computer Science and Electrical Engineering at Stanford University. She received a PhD in mathematics from the University of Michigan in 2014, and a BA in math and computer science from Swarthmore College in 2008; she was an NSF postdoctoral fellow at Carnegie Mellon University from 2014 to 2016. Her research interests include randomized algorithms, coding theory, dimension reduction, matrix completion, and sparse signal processing.

John Preskill, Richard P. Feynman Professor of Theoretical Physics at the California Institute of Technology, gave a lecture about Introduction to Quantum Information.
The lecture is the first of two parts, and was filmed at the Canadian Summer School on Quantum Information, held at the University of Waterloo in June of 2012.
Find out more about IQC!
Website - https://uwaterloo.ca/institute-for-quantum-computing/
Facebook - https://www.facebook.com/QuantumIQC
Twitter - https://twitter.com/QuantumIQC